Yamaha Hydra Drive problem

[SteveBlazye]

Good afternoon
I have just purchased a 33' Windy Mistral boat with a pair of Yamaha 420sti engines coupled to Yamaha hydra drives.
I had the legs fully serviced which included changing the oil and filters and inspecting them. All seemed fine
The last two times I've taken her out it runs perfectly for about 20 mins then i lose drive to the port engine. the engine revs but the prop doesn't turn. The drive to the leg is turning from the engine.
I returned to port each time and checked everything i can in the engine bay.. all linkages etc seem fine. After 30/40 minutes of sitting with the engines off though she starts up and drive is back again in both forward and reverse.
Any idea what this might be?
Thanks

 

[volvopaul]

Good afternoon
I have just purchased a 33' Windy Mistral boat with a pair of Yamaha 420sti engines coupled to Yamaha hydra drives.
I had the legs fully serviced which included changing the oil and filters and inspecting them. All seemed fine
The last two times I've taken her out it runs perfectly for about 20 mins then i lose drive to the port engine. the engine revs but the prop doesn't turn. The drive to the leg is turning from the engine.
I returned to port each time and checked everything i can in the engine bay.. all linkages etc seem fine. After 30/40 minutes of sitting with the engines off though she starts up and drive is back again in both forward and reverse.
Any idea what this might be?
Thanks

Depends who serviced them , I’d guess they have filled them with the wrong oil because they are hydraulic clutches , they have an oil pump inside , the wrong oil can cause low oil pressure which will allow the clutches to slip.

Or worse still the oil level too low , now do you have the level bottles on each engine ?

 

[SteveBlazye]

Thank you for your swift reply. They were serviced by Purbec marine in Poole. I have no reason to believe that they didn't use the correct oil. they filled with Yamalube GL5 SAE90 gear oil. I dont have level bottles i am afraid. After the service I took the boat for a run of about 50 miles without issue. The port engine did get hot at three quarters throttle though so i back off but there wasn't any drive problems. This has only happened on the last two short trips of about 10 miles.

 

[Ferris]

Is the prob bush slipping in the hub? Use tipp ex to mark bush/prop and see if it moves. No experience myself but it’s an easy one to rule out.

 

[NorthUp]

No external bottles to check the oil.
Its a regular occurrence on the yamaha legs, the oil pressure drops as they heat up, and then the clutches start slipping. Drive comes back with cooling.
Best case is the little oil filter is choked with swarf, but expect to need a new clutch pack and oil pump very soon. Sorry!

 

[NorthUp]

..and as Volvopaul says above the correct oil is crucial..

 

[Machaseo]

Take the Plastic cowal off the leg and remove the two Bolts holding the small plate and remove it. There is a mesh filter behind it.
check the filter for debris, this can partially block with metal filings.

 

[volvopaul]

There should be a gasket on the invoice, they would require that to clean the filter screen , no gasket , no clean , possibly overlooked .
Are Purbec agents ?